1. Field of the Invention
The present invention relates to broadband signal switching equipment comprising a crosspoint matrix which, in turn, comprises matrix input lines, each formed with two signal conductors, the matrix input lines being respectively connected, first of all, two different complementary outputs of an input digital signal circuit and, secondly, being connectible by way of crosspoints to matrix output lines which are each likewise formed with two signal conductors which lead to two signal inputs of an output amplifier circuit formed with a differential amplifier.
2. Description of the Prior Art
Recent developments in telecommunications technology have led to integrated services communications transmission and switching systems for narrow band and broadband communication services which provide light waveguides as transmission media in the region of the subscriber lines, both narrow band communication services such as, in particular, 64 kbit/s digital telephony, and broadband communication services such as, in particular, 140 Mbit/s picture telephony being conducted thereover, whereby narrow band signal switching equipment are provided side-by-side in the exchanges (preferably comprising shared-controlled devices as in the German Pat. No. 24 21 002).
In conjunction with a broadband signal time-division multiplex switching system whose crosspoints are utilized in time-division multiplex for a respective polarity of connections, it is known to connect respectively two lines with the assistance of a gate circuit that is switched on and off by a crosspoint-associated memory cell formed as a bistable D flip-flop, whereby this crosspoint-associated memory cell whose clock input is supplied with an appropriate clock signal is driven in only one coordinate direction, namely at its D input (Pfanneschmidt, "Arbeitsgeschwindigkeitsgrenzen von Koppelnetzwerken fur Breitband-Digitalsignale", Dissertation Braunschweig 1978, FIG. 6.7, FIG. 6.4). In view of a time-division multiplex factor of about 4-8 obtainable given a bit rate of 140 Mbit/s and of the involved circuit technology thereby required, however, fewer space-division switching equipment are currently preferred for switching broadband signals, the connections through-connected via the individual crosspoints being separated from one another therein in only spatial terms.
A pure broadband signal space coupling arrangement can be fashioned as a crosspoint matrix in CMOS technology provided with input amplifiers and output amplifiers in whose crosspoints the switch elements are respectively controlled by a decoder-controlled, crosspoint-associated holding memory cell, whereby the switch elements are each fashioned as a CMOS transfer gate (CMOS transmission gate) (ISS 84 Conference Papers 23 Cl, FIG. 9); the crosspoint-associated holding memory elements of a pure space switching multiple can be selected in two coordinates proceeding from a row decoder and from a column decoder, being respectively selected via a row-associated or, respectively, column-associated selection line (Pfannschmidt, op. cit. FIG. 6.4). Inversely, however, it is also possible to integrate crosspoint-associated address decoder elements (logic elements) into the crosspoint matrix itself, whereby these address decoder elements are charged with crosspoint addresses proceeding from external address registers, i.e. from address registers arranged outside of the actual crosspoint matrix (see, for example, Kunze, "TIDES: A NEW CONCEPT IN TIME DIVISION ELECTRONIC SWITCHING", Communications presentees au Colloque INTERNATIONAL de COMMUNICATION ELECTRONIQUE, Paris, 1966, EDITIONS CHIRON, pp. 301-312, FIG. 4 and FIG. 5).
A broadband signal switching equipment comprising a crosspoint matrix in ECL technology is also known (from FERNSEH UND KINO-TECHNIK, Vol. 38, No. 4, 1984, pp. 137-143, FIGS. 3-5), this crosspoint matrix respectively comprising matrix input lines formed with two signal conductors, the matrix input lines being connected, first of all, to respectively two complimentary outputs of a row input amplifier and, secondly, being connectable by way of crosspoints to matrix output lines likewise respectively formed with two signal conductors which respectively lead to the two signal inputs of a column output amplifier formed by a differential amplifier. The crosspoints are thereby constructed in a bipolar current switch technology (also referred to CML current mode logic) in accordance wherewith a current supplied by a current source switchable by a through-connection or, respectively, inhibit signal, is switched into the one or the other branch of a differential amplifier formed with two emitter-coupled transistors, being switched thereinto based on the measure of the matrix input signal. Disturbing signals which can proceed to the output in the inhibited condition of such a crosspoint by way of a depletion layer capacitance of the collector-base diodes are thereby to be attenuated by a neutralization circuit requiring two additional transistors having exactly the same dimensions.